Disclosed herein is a toner composition suitable for use in single component development processes.
The formation and development of images on the surface of photoconductive materials by electrostatic means is well known. The basic electrophotographic imaging process, as taught by C. F. Carlson in U.S. Pat. No. 2,297,691, entails placing a uniform electrostatic charge on a photoconductive insulating layer known as a photoconductor or photoreceptor, exposing the photoreceptor to a light and shadow image to dissipate the charge on the areas of the photoreceptor exposed to the light, and developing the resulting electrostatic latent image by depositing on the image a finely divided electroscopic material known as toner. Toner typically comprises a resin and a colorant. The toner will normally be attracted to those areas of the photoreceptor which retain a charge, thereby forming a toner image corresponding to the electrostatic latent image. This developed image may then be transferred to a substrate such as paper. The transferred image may subsequently be permanently affixed to the substrate by heat, pressure, a combination of heat and pressure, or other suitable fixing means such as solvent or overcoating treatment.
Numerous processes are within the purview of those skilled in the art for the preparation of toners. Emulsion aggregation (EA) is one such method. Emulsion aggregation toners can be used in forming print and/or xerographic images. Emulsion aggregation techniques can entail the formation of an emulsion latex of the resin particles by heating the resin, using emulsion polymerization, as disclosed in, for example, U.S. Pat. No. 5,853,943, the disclosure of which is totally incorporated herein by reference.
Two exemplary emulsion aggregation toners include acrylate based toners, such as those based on styrene acrylate toner particles as illustrated in, for example, U.S. Pat. No. 6,120,967, and polyester toner particles, as disclosed in, for example, U.S. Pat. Nos. 5,916,725 and 7,785,763 and U.S. Patent Publication 2008/0107989, the disclosures of each of which are totally incorporated herein by reference.
In some single component developers (i.e., developers in which a toner is used without a carrier), the toner can exhibit disadvantages such as deposition of wax or silica onto the developer roll over time, leading to functional defects in the hardware and eventual print defects. Other difficulties commonly encountered with developers containing relatively large size external additive particles include poor toner flow characteristics, image deletions, and image fading. Accordingly, while known materials are suitable for their intended purposes, a need remains for toners suitable for use in single component development systems that exhibit low melt. In addition, a need remains for toners suitable for use in single component development systems that exhibit desirable fusing characteristics. Further, a need remains for toners suitable for use in single component development systems that exhibit reduced buildup on the developer roll of materials such as pigment, silica, and wax. Additionally, a need remains for toners suitable for use in single component development systems that exhibit desirable or improved charging stability. There is also a need for toners suitable for use in single component development systems that exhibit reduced fuser contamination. In addition, there is a need for toners suitable for use in single component development systems that exhibit desirable flow characteristics. Further, there is a need for toners suitable for use in single component development systems that produce uniform images. Additionally, there is a need for toners suitable for use in single component development systems that produce high yield of toner from the toner cartridge. A need also remains for toners suitable for use in single component development systems that exhibit improved image quality while also enabling improved printing speed.